This application claims the benefit of the Korean Application No. P2001-75457 filed on Nov. 30, 2001, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an optical projection system using a color drum.
2. Discussion of the Related Art
Lately, as satellite and digital broadcastings are promoted in earnest, demands and interests for a wide-screen display having high resolution are increases. Hence, the expectation and role of projection/projector become important. Besides, image information for high brightness and colorfulness as well as high resolution is strongly demanded, whereby many efforts are made to research and develop an inexpensive optical system having high photo-efficiency.
The products of the related art mostly use the three plate system, thereby increasing a product cost. Hence, the single plate system is tried to use.
FIG. 1 illustrates a structural diagram of a single-plated optical projection system according to a related art.
Referring to FIG. 1, a light from a lamp as a light source 1 consists of 50% P-waveform and 50% S-waveform and is equalized through FEL (fly eye lens) 2.
A system including a reflective LCD(liquid crystal display) uses the P- or S-waveform only. The S-waveform has excellent optical characteristics to use widely.
In order to increase a photo-efficiency, the waveform is passed through a PBS array 3 to turn into 75% S-waveform and 25% P-waveform. The photo-efficiency increases if 100% S-waveform is made. Yet, the current component technology enables to provide about 75% S-waveform. The S-waveform is reflected on a surface of PBS 5 to be incident on a panel 7, and P-waveform passes through the PBS 5 to abandon.
The S-waveform entering the panel 7 is modulated by liquid crystals to be expressed as a gray level and is then reflected thereon. The S-waveform passes the PBS 5 and a projection lens 8 to throw an image on a screen 9. Thus, the projection system is constructed.
Even if such a single-plated system uses a single panel only to be advantageous in aspect of cost, R, G, and B should be sent sequentially through a color separating means of a color switch or a color wheel (color sepuential). Hence, photo-efficiency is ⅓ of that of the three-plate system to degrade brightness. In order to implement the same brightness of the three plate system, a lamp(light source) of large capacitance is required. Besides, as the lamp capacitance increases, endurance decreases abruptly.
Moreover, if the color wheel or color switch is used, a light of the lamp should not be applied to the panel during an addressing time for applying data(gray levels) to the entire pixels of the panel and the time for which liquid crystals react. Such a fact should be considered. And, since the abandoned 25% P-waveform is unable to use, the photo-efficiency is substantially reduced below ⅕.
In order to overcome such disadvantages, a method of increasing a system photo-efficiency using a revolving prism is tried. Yet, an optical system for such a method is complicated to reduce reliance as well as fails to provide high photo-efficiency substantially due to its structure limitation.
Accordingly, the present invention is directed to an optical projection system that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an optical projection system having a simple structure by scrolling a light of each wavelength efficiently on a panel by preventing a color shift by adjusting a width of a color band on a color drum surface properly.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an optical projection system using a color drum according to the present invention includes the color drum outputting an incident light through a predetermined number of color bands on a drum plane to display wherein a light outputted from an end of a light projecting plane outputting the incident light has an incident angle equal to or smaller than 30xc2x0 on the color band.
Preferably, the optical projection system includes a light source, a rod lens receiving the light from the light source, the rod lens having the light projecting plane inside to output the received light, a color drum having the predetermined number of the color bands on a color drum plane to output the incident light from the light projecting plane through the color bands, a panel receiving the light outputted from the color drum to modulate to output the received light in accordance with a gray level, and a screen receiving the modulated light from the panel to display.
More preferably, the number of the color bands of the color drum is at least six.
More preferably, the optical projection system further includes an FEL(fly eye lens) receiving to equalize the light incident from the light source.
More preferably, the optical projection system further includes a PBS array polarizing to output the light outputted through the color drum.
More preferably, the optical projection system further includes a PBS receiving the light outputted from the PBS array and the PBS reflects and transmits the received light from the PBS array in accordance with polarization to input to the panel.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.